1. Field of the Invention
The invention is directed to a protective pipe for a piston-cylinder unit.
2. Prior Art
A piston rod of a piston-cylinder unit is a component whose surface must be shielded from dirt so that a seal closing the cylinder is not destroyed by fine particles in the dirt.
Protective pipes made of plastic have become popular for reasons having to do with weight. The protective pipe has a base that is often supported on a shoulder of the piston rod. The base is frequently produced as an annular metal disk which is connected by positive engagement to a plastic pipe. The metal base provides for good dimensional stability of the plastic pipe but adds considerably to the cost of the protective pipe. In this connection, reference is had to DE 28 50 051 A1; DE 19 51 753 U, or DE 19 51 754 U.
DE 37 35 058 A1 discloses a one-piece protective pipe made of plastic in the construction shown in FIG. 2. Starting from a nominal diameter, the protective pipe has a conical transitional area extending radially inward and which opens into a horizontally extending clamping surface that contacts a shoulder of the piston rod. While this protective pipe made entirely of plastic has a cost advantage, it cannot achieve the qualities of a protective pipe with a metal base with respect to dimensional stability.
DE 82 28 262 U1 discloses in FIG. 1 a one-piece plastic protective pipe that extends parallel to the piston rod on a longitudinal portion in the area of a screw-on part and is radially centered in this way.